Delta-Sigma Modulator Integrator Calibration
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Solution Overview
Problem
Continuous-time delta-sigma modulators in integrated circuits face performance degradation and instability due to inaccuracies in integrator time constants, which are temperature-dependent and deviate from design values, leading to noise-shaping behavior deviations and potential system failure.
Innovation Solution
A calibration circuit that uses an auxiliary delta-sigma modulator to estimate and adjust the time constants of integrators in the primary modulator, employing an estimator circuit and controller to generate correction signals based on error sequences and output sequences, ensuring accurate time constant matching and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If continuous-time integrators are used in the loop filter, then the modulator can process continuous-time signals directly, but the integrator time constants deviate from design values due to temperature drift and component tolerances
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the time constants of the continuous-time integrators based on measured performance. The system measures the actual time constants at different temperatures and modifies the integrator parameters (resistor or capacitor values) to compensate for deviations, thereby maintaining accurate noise-shaping behavior across temperature variations while preserving continuous-time signal processing capability
Solution Approach 2:
The patent implements feedback by measuring the actual time constants of the integrators and using this information to adjust the loop filter parameters. The system continuously monitors performance and feeds back correction signals to the integrator configuration, enabling automatic compensation for temperature drift and component tolerance effects without requiring manual recalibration
2Ease of manufacture
If integrator time constants are not calibrated, then the device is simpler and faster to manufacture, but the noise-shaping behavior deviates from the target response
Solution Approach 1:
The patent applies preliminary action by performing time constant measurements and calibrations during the manufacturing or initialization phase. The system pre-determines the actual time constants of the integrators and stores compensation parameters that are applied during operation, thereby ensuring accurate noise-shaping behavior without requiring complex real-time adjustment mechanisms or slowing down the manufacturing process
3Reliability
If the integrator time constants are adjusted to compensate for temperature drift, then the stability and performance are improved, but additional calibration circuits and control logic are required
Solution Approach 1:
The patent applies self-service by enabling the modulator to automatically measure its own time constants and perform self-calibration without external intervention. The system includes built-in measurement circuits that can determine the actual time constants during normal operation or initialization, and automatically adjusts the integrator parameters based on these measurements, thereby improving reliability while minimizing the addition of external calibration equipment
Data Source
AI summary
A primary delta-sigma modulator converts a continuous-time input signal into a discrete-time output sequence. A calibration circuit comprising an auxiliary delta-sigma modulator estimates percentage error in an integrator time constant and adjusts the time constant of at least one integrator in the primary delta-sigma modulator accordingly. The auxiliary delta-sigma modulator and the primary delta-sigma modulator use integrators with substantially similar circuit designs. The percentage error in the time constant of the integrator in the auxiliary delta-sigma modulator, and correspondingly the percentage error in time constant of the integrator in the primary delta-sigma modulator, is estimated by injecting a calibrating sequence into the auxiliary delta-sigma modulator and examining a correlation between an error sequence and an output sequence of the auxiliary delta-sigma modulator.